1. Field of the Invention
The present invention relates generally to bolsters that are used in construction activities for the support of post-tension cables, rebars or mesh. More particularly, the present invention relates to upper beam bolsters that are designed for support on underlying layers of mesh and rebar or on slab-on-grade surfaces. Additionally, the present invention relates to upper beam bolsters formed integrally together of a polymeric material.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Bolsters are commonly used in the construction industry for the support of post-tension cables, rebars, or mesh above a surface. Typically, when such materials are used, they must be supported above the surface when the concrete is poured. These bolsters are used with poured decks. In normal use, the bolster is positioned on the deck and includes a beam which extends across a plurality of leg members. This beam is formed so as to contact and support the rebar while the base of the bolster rests on the deck or on a grade. When the concrete is poured, the bolster will support the rebar a proper distance above the bottom surface.
In normal use, such bolsters are preformed so that they can be installed quickly and easily upon the deck. Conventionally, the preformed bolster will have a plurality of leg members and a steel rod welded to a top surface of each of the leg members. The rod will serve as a receiving area for the rebar. Conventionally, these bolsters are formed in preset lengths. If it is necessary to extend the bolster across a long surface of the deck, then the ends of the beams of adjacent bolsters will be wired together such that the bolsters are in an end-to-end relationship.
The most common bolster that is employed is a metal bolster manufactured by Meadow Steel Products of Tampa, Fla. This bolster has a plurality of inverted U-shaped leg members having outwardly extending foot portions. A rigid tubular rod having a slight waveform pattern formed thereon is welded to the middle of the inverted U-shaped leg members. Each of the leg members is generally arranged in parallel relationship to each other. The feet of each of the leg members will rest on the deck while the rebar is supported. After the concrete has solidified, and the deck is removed, the bottom surfaces of the feet will be exposed. As such, it is necessary to coat the feet with an anti-rust material. Alternatively, stainless steel material can be employed for the leg members and their associated feet.
Corrosion and cost are major problems affecting the bolster of Meadow Steel Products. In order to form such a bolster, a great deal of manufacturing must take place, including metal forming, bending, dipping, and welding. These activities, along with the cost of the material used to form the bolster, make the cost of the bolster relatively expensive. If the bolster is not coated or made of a stainless steel material, then corrosion can adversely affect the product. This corrosion can even occur when the metal is coated.
In the past, various attempts have been made to create bolsters of plastic material that can serve the purposes of the bolster of Meadow Steel Products. In general, such efforts have resulted in plastic chairs that are ineffective, cumbersome to use, or unable to properly withstand the forces imparted by the rebar upon the bolster. One such plastic bolster, manufactured by Conac, includes a central beam which is integrally formed with a plurality of leg members. Each of the leg members extends downwardly so as to present a flat surface to the underlying deck. No feet are provided which allow the bolster to be stapled to the deck. Additionally, the configuration of this Conac bolster allows for easy deformation. It is very difficult and time consuming to join lengths of the Conac bolster together. This plastic bolster is often broken, collapsed, or tipped over in actual use. The base of such a bolster has only a very small area of contact with the deck. As such, these plastic bolsters lack the strength and ability to withstand the loads imparted to them.
U.S. Pat. No. 5,664,390, issued on Sep. 9, 1997 to the present inventor, describes a bolster for use in construction. This bolster has a plurality of leg members arranged in parallel relationship and a beam integrally formed with the plurality of leg members and extending across the plurality of leg members. Each of the plurality of leg members has a foot for contacting the underlying surface. Each of the leg members includes a central body portion, a first leg extending downwardly from one side of the central body portion and a second leg extending downwardly from an opposite side of the central body portion. The foot is formed at an end of each of the first and second legs opposite the central body portion. The foot includes a plurality of pin-like projections extending outwardly from a bottom surface thereof. This bolster is of a type for stapling and fixed attachment to an underlying deck. However, under certain circumstances, it would be desirable to be able to use these bolsters for “upper beam” purposes. Upper beam bolsters are often used upon the top of mesh or layers of strands. The upper beam bolsters are commonly used in highway construction where multiple layers of steel are laid out. Under other circumstances, a widened or flat base is required for slab-on-grade construction. The relatively small and narrow feet would sink into sand or dirt if the bolsters of U.S. Pat. No. 5,664,390 were used for “upper beam” purposes. In other circumstances, upper beam slab bolsters are used on corrugating steel decking so as to be in flat surface-to-surface contact with such steel flat surfaces. As such, a need developed so as to allow the bolster of U.S. Pat. No. 5,664,390 to be properly adapted for upper beam bolster purposes.
U.S. Pat. No. 6,775,954, issued on Aug. 17, 2004 to the present inventor, describes such a bolster properly adapted for upper beam bolster purposes. The bolster has a plurality of leg members arranged in generally parallel spaced relationship to each other, a beam integrally formed with the plurality of leg members and extending transversely across the leg members, a first plate affixed to one side of the plurality of leg members and a second plate affixed to an opposite side of the plurality of leg members. Each of the plates has a generally flat bottom surface. A clip is provided on the plates for fixedly attaching the plates to respective feet of the leg members. While the article associated with U.S. Pat. No. 6,775,954 proved successful, connecting the plates with the feet of the leg members is a labor-intensive process. As such, a need has developed for an upper beam slab bolster which does not require assembly.
U.S. Pat. No. 6,772,571, issued on Aug. 10, 2004 to the present inventor, teaches a bolster for use in construction that has a plurality of leg members arranged in a generally parallel spaced relationship, a beam integrally formed with the plurality of leg members which extends transversely across the plurality of leg members, and a plate affixed to the bottom of the plurality of leg members. The plate has a generally flat bottom surface. The plate has at least one clip formed on the top surface receiving a foot associated with at least one of the leg members.
U.S. Pat. No. 7,284,354, issued on Oct. 23, 2007 to the present inventor, describes a bolster for use in construction. The bolster has a beam, a first plurality of leg members on one side of the beam, a second plurality of leg members on an opposite side of the beam, a first plate having a receptacle on one side thereof and a second plate having a receptacle on one side. The receptacle of the first plate receives a portion of the first plurality of leg members therein. The receptacle of the second plate receives a portion of the second plurality of leg members. The receptacles have a generally C-shaped cross section for resiliently contacting surfaces of the respective leg members. The plate is integrally formed of an extruded polymeric material.
U.S. Pat. No. 7,373,764, issued on May 20, 2008 to the present inventor teaches a similar extruded upper beam slab bolster for use in construction. The bolster has a beam, a first plurality of leg members on one side of the beam, a second plurality of leg members on an opposite side of the beam, and a plate having a first receptacle on one side and a second receptacle on the opposite side. The first receptacle receives a portion of the first plurality of leg members therein. The second receptacle receives a portion of the second plurality of leg members therein. The plate is integrally formed of an extruded polymeric material.
U.S. patent application Ser. No. 12/349,389, filed on Jan. 6, 2009 by the present inventor describes an extruded upper beam slab bolster that has a snap-fit arrangement between segments of the bolster. The bolster has a beam, a pair of spaced apart foot members, a first plurality of leg members on one side of the beam, and a second plurality of leg members on an opposite side of the beam. The first plurality of leg members are connected at one end to the beam and at the opposite end to one of the pair of spaced apart foot members. The second plurality of leg members are connected at one end to the beam and at the opposite end to the other of the pair of spaced apart foot members. The beam, pair of spaced apart foot members and first and second pluralities of leg members are integrally formed together of a polymeric material. Multiple lengths of bolster may be joined together in a snap-fit engagement.
It is an object of the present invention to provide an upper beam slab bolster that is corrosion-proof and relatively inexpensive.
It is another object of the present invention to provide an upper beam bolster that can withstand the forces imparted to it.
It is a further object of the present invention to provide an upper beam slab bolster that is integrally formed together through injection molding processes.
It is still a further object of the present invention to provide an upper beam bolster that is easy to manufacture and easy to use.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.